The present invention relates generally to a welding apparatus and, more particularly, a welder having a convenient grounding device that facilitates the assembly of the welding apparatus.
Portable welding units transportable to a work site are known. Typical of such known units include a lightweight enclosure consisting of a sheet metal material, such as aluminum or other metal and which metal enclosure has a front panel and a rear panel at the ends of the enclosure to contain the various components of the welder therein and also includes a base that underlies the enclosure. In general, the front and rear panels, as well as the base of such welding apparatus is constructed of a molded plastic material.
With such welders it is important that certain metal components be grounded. Since the enclosure itself for such welding apparatus is constructed of metal, it is necessary that such enclosures be properly grounded to comply with applicable standards in order to protect the user of the apparatus.
With the joining of two structural components, one common method of grounding an enclosure or panel is through the use of a screw that passes through a clearance hole in the component to be grounded. The underside of the head the screw has a paint-cutting ring such that the tightening of the screw removes paint under the screw head and creates a good electrical contact with the component to be grounded. The screw is then threaded into a component that is already grounded and the screw connects the two components both electrically and mechanically. However, as is evident, the use of such a grounding screw is limited to applications where both of the components are metal so that one component is basically grounded through the other.
Another common method of providing a ground to a metal component, such as an enclosure, is to use a machine screw that passes through a clearance hole in the component to be grounded and a nut is secured on the other side of that component. A ring terminal is placed on top of the nut and still another nut is placed on top of the ring terminal. The nut that touches the component to be grounded makes contact therewith and the ring terminal can be attached to a wire that is connected to ground. While effective, the procedure is rather cumbersome and, therefore, is time consuming in the assembly line operations used to assemble equipment such as welding apparatus.
Finally, as a further grounding method, a sheet metal component may be grounded by bending or welding a tab into the sheet metal component and that tab is manufactured in such as way as to accept a friction connector that is, in turn, connected to a wire that leads to a ground connection. Again, the grounding procedure is not particularly simple and can be a time-consuming action in the assembly of welding apparatus.
Therefore, it would be advantageous to have a simple means of grounding a metal structural component such as the enclosure of a welding apparatus, and which can be carried out with a minimum of disruption or time consumption during the assembly line production of such apparatus and which can be utilized where plastic components are a structural part of the apparatus.
The present invention is directed to an improved grounding means for a welding apparatus.
In a preferred embodiment, and as will be specifically described herein, the welding apparatus itself is comprised of a metal enclosure that houses the various components that are utilized in providing a variable power supply to carry out the welding process. The enclosure has a pair of end panels, that is, there is a front panel and a rear panel that are affixed to the enclosure to contain those components therein. The front and rear panels are preferable constructed of a molded plastic material.
Each of the panels includes a receptacle that is molded into the panel. The receptacle has a slotted opening formed therein. In accordance with the invention, a grounding tab is affixed within the receptacle and is fitted therein with an interference fit so that the grounding tab is securely affixed to the receptacle. In the preferred embodiment, the grounding tab has a generally flat, planar metal body with lateral edges and each of the lateral edges has a notch formed therein that allows the grounding tab to be forced into the receptacle but which catches and bites into the sides of the slotted opening to basically prevent the removal of the grounding tab from the receptacle after it has been affixed therein.
The grounding tab also has at least one prong, and preferably a pair of prongs, that extend outwardly from the planar body such that the distal ends of the prongs are bent upwardly to make a forceful electrical contact with the internal surface of the metal enclosure when the end panels are affixed to the enclosure. The grounding tab also has a friction terminal extending outwardly therefrom and which is adapted to be connected to an electrical connector having a grounding wire so that a grounding wire can easily and readily be electrically connected to the grounding tab.
In a preferred embodiment there is also a threaded hole formed in the flat, planar body of the grounding tab. As such, when the end panels are affixed to the metal enclosure, a screw can be passed through a hole in the metal enclosure and then screwed into the threaded hole in the grounding tab to make a second electrical contact between the metal enclosure and the grounding tab as well as to assist in the actual affixation of the end panels to the enclosure.
Thus, with the use of the grounding tab of the present invention, the grounding tab creates two good electrical connections between the metal enclosure and the grounding tab and, accordingly, a ground wire can readily be attached to the friction terminal of the grounding tab and that wire can ground the metal enclosure by connecting to a further ground, such as a ground wire of the electrical supply cable.
With the aforementioned grounding tab and receptacle, it can be seen that the assembly of the welding apparatus is simplified. That is, the grounding tab can be pre-assembled to the receptacle and, during the assembly of the welding apparatus, a ground wire can be quickly, and without tools, affixed to the friction terminal by a standard electrical connector on that ground wire. When the end panels are thereafter affixed to the enclosure, there are two good electrical ground connections made between the metal enclosure all the way to the ground wire and the ground wire can thereafter be connected to a circuit board and eventually provide a conductive path to a ground wire of an electrical supply cable.